Research: Cosmology

Cosmological research in Birmingham concentrates on galaxy clusters as probes of "dark cosmology", i.e. dark matter, dark energy, and gravity theory. As a class of astronomical object, clusters are particularly well suited to dark cosmology studies because

their internal structure is dominated by dark matter

the rate at which they grow with cosmic time is regulated by the expansion rate of the universe and is therefore sensitive to dark energy

they are sensitive via "standard ruler" tests directly to the geometry of the universe

measurements of the space- and time-like gravitational potentials are in principle feasible.

It is a truism, that attempting to study fundamental physics via astronomical observations requires that the cosmological signal be disentangled from the numerous astrophysical processes at play; arguably this is most true for "cluster cosmology". This is therefore a very challenging and exciting intellectual endeavour, under-written by several fundamental certainties, including that we will learn important new physics (inevitably a mixture of cluster physics and cosmology), and that no technique can constrain dark cosmology on its own due to strong parameter degeneracies.

Today our cosmological research concentrates on exploiting the superb dataset (HST, Subaru, Chandra, XMM-Newton, SZA) assembled by Smith and collaborators as part of the Local Cluster Substructure Survey (LoCuSS). We increasingly turn our attention to including lower mass and higher redshift systems in collaboration with our colleagues in the Ultimate XMM-Newton Extragalactic Survey (XXL). We have also recently joined the Euclid Consortium, and are active supporters of potential future involvement of the UK/EU in the Large Synoptic Survey Telescope (LSST). Our LoCuSS and XXL studies will be increasingly geared towards these future facilities.